1. Field of the Invention
The present invention relates to a light source apparatus that uses LEDs as the light source and, in particular, to a light source apparatus that suppresses an increase in the temperature of the LEDs.
2. Description of the Background Art
Conventionally, a discharge lamp has been widely used as the light source of a projector type image display apparatus. In recent years, advances in the light-emitting diode (hereinafter referred to as LED) technology has brought about enhanced output brightness of the LEDs which is enough to serve as the light source of the projector type image display apparatus. Because brightness characteristics of the LEDs vary depending on the temperature of the LEDs, it is necessary to control the temperature so as to be equal to or lower than a proper temperature. An increase in the temperature of the LEDs to be equal to or higher than a prescribed value invites a reduction in brightness, and also a significant reduction in service life.
However, a heat generating amount of each LED light source varies depending on colors, and it is difficult to cool LEDs of different colors by an identical heatsink. Additionally, though a large-sized cooling structure in which heatsinks and fans are used is required to cool the LEDs, it is desirable to implement the cooling structure while saving space as much as possible, in consideration of a reduction in size of the apparatus.
In order to address such a problem, what are available in the conventional techniques are: the one that brings a plurality of LEDs into contact with a heatsink so as to uniformly cool the LEDs; the one that uses a Peltier element; and the one that conducts central cooling by having a heat pipe or the like perform heat transport. For example, Japanese Patent Application Laid-Open No. 2004-362900 discloses the one that evenly cools the LEDs, Japanese Patent Application Laid-Open Nos. 2008-192940 and 2006-253274 disclose the cooling unit using the Peltier element, and Japanese Patent Application Laid-Open Nos. 2006-059607, 2005-316337 and 2004-259841 disclose a module structure using the heatsink, fans, and the heat pipe.
While various structures as described above are available as means for cooling the LEDs, there are no light source apparatuses that determines the cooling order based on the difference in the upper limit temperature among the LED light sources, or light source apparatuses that have cooling unit structured to cool a plurality of heatsinks altogether for achieving a reduction in size.